Решите пример:
(2целых 5/9 - 1целая 20/21) : 1целую 8/49 + 1целая 8/9 : 6 =_______

(9*2+5/9-21*1+20/21):49*1+8/49+9*1+8/9:6=(23/9-41/21):57/49+17/9:6=(7*23/63-3*41/63):57/49+17/9:6=(161/63-123/63):57/49+102/9=38/63:57/49+102/9=38*49/63*57+102/9=1862/3591+102/9=1862+399*102/3591=42560/3591=12целых468/3591